Facebook decided Friday to allow a type of paid political message that had sidestepped many of the social network's rules governing political ads, in a reversal that highlights difficulties tech companies and regulators have in keeping up with the changing nature of paid political messages.

Facebook Inc. said Thursday that it will continue to allow political ads on its platform including Instagram, despite possible false information in those ads run by politicians.

Twitter announced an end Wednesday to political campaign and issue ads on its service, calling it an important step in reducing the flow of election-related misinformation.